The correct answer involves placing the NAT device in a public subnet with a route to an internet gateway and configuring the route tables of the private subnets to point all default traffic (0.0.0.0/0) to that NAT device. This works because the NAT gateway, residing in a public subnet with direct internet access via the internet gateway, translates private IP addresses to its own public IP for outbound traffic, while the private subnet route tables ensure every outbound packet is forwarded to the NAT device for centralized logging and filtering. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of VPC routing and NAT architecture for security control—a common trap is assuming a transit gateway or proxy is needed, but the key is that a NAT device in a public subnet with an internet gateway is sufficient for outbound-only internet access from private subnets. Remember the memory tip: “NAT needs a path to the outside world—public subnet and IGW—while private subnets just need a route pointing to the NAT.”
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A security engineer is designing a network architecture in AWS. The engineer needs to ensure that all outbound traffic from a VPC goes through a centrally managed NAT device for logging and filtering. The VPC has multiple private subnets. Which TWO steps are required to accomplish this? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a route table for the private subnets with a default route (0.0.0.0/0) pointing to the NAT device.
Option B and D are correct. Configuring the route tables to point to the NAT device ensures traffic goes through it. Placing the NAT device in a public subnet with an internet gateway allows it to reach the internet. Option A is wrong because a transit gateway is not needed. Option C is wrong because a proxy is not required. Option E is wrong because a gateway endpoint is for S3/DynamoDB, not internet traffic.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Deploy an HTTP forward proxy in the public subnet.
Why it's wrong here
A proxy is not required; a NAT device can perform network address translation.
✓
Create a route table for the private subnets with a default route (0.0.0.0/0) pointing to the NAT device.
Why this is correct
This routes outbound traffic from private subnets to the NAT device.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Infrastructure Security — This question tests Infrastructure Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Create a route table for the private subnets with a default route (0.0.0.0/0) pointing to the NAT device. — Option B and D are correct. Configuring the route tables to point to the NAT device ensures traffic goes through it. Placing the NAT device in a public subnet with an internet gateway allows it to reach the internet. Option A is wrong because a transit gateway is not needed. Option C is wrong because a proxy is not required. Option E is wrong because a gateway endpoint is for S3/DynamoDB, not internet traffic.
What should I do if I get this SCS-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is designing a VPC with public and private subnets in two Availability Zones. They need to ensure that instances in the private subnets can access the internet for software updates but cannot be directly accessed from the internet. Which AWS service or feature should be used to meet this requirement?
medium
✓ A.NAT Gateway
B.VPC Peering
C.AWS VPN
D.Internet Gateway
Why A: Option B is correct because a NAT Gateway allows instances in private subnets to initiate outbound traffic to the internet while preventing inbound traffic from the internet. Option A is wrong because an Internet Gateway is used for public subnets and allows inbound traffic. Option C is wrong because a VPN connection is for site-to-site connectivity, not internet access. Option D is wrong because a VPC Peering connection connects VPCs, not to the internet.
Variation 2. A security engineer is designing a VPC with public and private subnets in two Availability Zones. The company requires that all outbound traffic from private subnets to the internet must go through a single, centrally managed NAT gateway. Which combination of resources and route table entries should be used?
medium
✓ A.A single NAT gateway in a public subnet, and a default route (0.0.0.0/0) in each private subnet route table pointing to that NAT gateway.
B.A single NAT gateway in a private subnet, and a default route in each private subnet pointing to the NAT gateway.
C.One NAT gateway per private subnet, each with a route to an internet gateway.
D.One NAT gateway per Availability Zone, with routes to the internet gateway.
Why A: Option C is correct because placing a single NAT gateway in a public subnet and adding a default route to the NAT gateway in the private subnet route tables achieves the requirement. Option A is wrong because each private subnet needs its own route entry. Option B is wrong because using multiple NAT gateways defeats central management. Option D is wrong because NAT gateways cannot be placed in private subnets.
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This SCS-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SCS-C02 exam.
Question Discussion
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